Recently, various materials having a physiological function have been proposed, and many health foods containing these materials are available in the market. Among them, polyphenols are known to have an antioxidative activity and are considered as an important component of the health foods because of their expected effects such as antiarteriosclerotic effect, antiallergic effect and augmentation effect of blood stream.
However, since many polyphenols are hardly soluble in water, it is difficult to use them for foods and drinks, and the like.
The technique for solubilizing a hardly water-soluble polyphenols into water has been investigated. For example, it is reported that a method for solubilizing hesperidin by subjecting hesperidin and hesperidin-sugar adduct to a heat treatment at 100 to 180° C. in the presence of an aqueous medium (Patent Document 1).